There have so far been proposed a liquid crystal projector and liquid crystal projection type television set, in which an image on a liquid crystal panel used as an optical switching device is projected onto a screen for display in an enlarged scale through a projection optical system. These apparatuses are thin, lightweight and capable of displaying a sharp image.
A liquid crystal display capable of displaying a sharper projected image has been proposed in the Japanese Patent Laid Open No. 161097 of 1998 (also referred to as “Patent Document 1” herein). FIG. 1 schematically illustrates the liquid crystal display disclosed in the Patent Document 1. The liquid crystal display is generally indicated with a reference numeral 100, and includes dichroic mirrors 112B, 112R and 112G which separate parallel white light L1 incident thereupon from a white light source into blue (B) light, red (R) light and green (G) light, an LCD (liquid crystal display) panel 120 to intensify each of the B light, R light and G light separated by the dichroic mirrors 112B, 112R and 112G, and a projection lens 130 to condense and combine the B light, R light and G light coming from the LCD panel 120 on a screen 140, as shown in FIG. 1.
The dichroic mirrors 112B, 112R and 112G are fixed to form a small angle with each other. They separate the white light L1 into the B light, R light and G light for incidence upon the LCD panel 120 at different angles, respectively.
As shown, the LCD panel 120 includes a pixel substrate 121 having multiple pixel electrodes formed thereon, an opposite substrate 122 having opposite electrodes and micro lenses formed thereon, and a liquid crystal layer 123 provided between the pixel substrate 121 and opposite substrate 122.
FIG. 2 is an illustration, enlarged in scale, of the sectional structure the LCD panel 120 included in the liquid crystal display 100. As shown in FIG. 2, the pixel substrate 121 includes a glass substrate 121a, B-, R- and G-light pixel electrodes 121B, 121R and 121G disposed regularly from bottom to top on one side (input side in the drawing) of the glass substrate 121a, and a black matrix 121b formed on the glass substrate 121a and including TFT etc. (not shown) functioning as a switching device to apply a voltage corresponding to an image signal to each of the pixel electrodes 121B, 121R and 121G. Each TFT has a gate, drain and source (not shown) made of polysilicon, for example. Of these electrodes, the gate is connected to an address wire extending vertically in the drawing, source is connected to a data wire extending perpendicularly to the plane of the drawing and the drain is connected to each of the pixel electrodes 121B, 121R and 121G. By selectively applying an image signal voltage to a pixel electrode selected by the address and data wires, the alignment of liquid crystal molecules in the liquid crystal layer 123 between the pixel electrode and opposite electrode 122d is changed to change the direction of polarization of light passing by the liquid crystal molecules.
On the other hand, the opposite substrate 122 includes a glass substrate 122a, a micro lens array 122b formed on one end portion of the glass substrate 122a, a cover glass 122c disposed close on the micro lens array 122b, and an opposite electrode 122d formed on the cover glass 122c. 
The opposite electrode 122d is a transparent electrode formed over, or on a necessary area of, the cover glass 122c and has a fixed potential.
The micro lens array 122b is formed as a graded index lens by the selective ion diffusion method, for example. Each of micro lenses (ML) forming together the micro lens array 122b is usually formed as a semi-cylindrical lens whose axis extends perpendicularly to the plane of the drawing. However, it may be an ordinary spherical lens or a curved lens similar to the spherical lens.
For reference's sake, the micro lens array 122b is formed from micro lenses disposed for the three pixel electrodes 121B, 121R and 121G, respectively, on the pixel substrate 121. B-, R- and G-light beams incident upon the micro lenses from three different directions are condensed for incidence upon the pixel electrodes 121B, 121R and 121G respectively, through the liquid crystal layer 123.
In the liquid crystal display 100 constructed as above, the micro lenses disposed with a pitch corresponding to the TFT pixel pitch are associated in one-to-one relation with the TFT pixels, respectively, so that the light supposed not to pass by the TFT light shield because it is reflected by the latter can be polarized to improve the transmittance.
Normally, the projector should have two performances: a high transmittance and contrast. In the liquid crystal display 100, the micro lens array 122 provided permits to design smaller TFTs which will possibly cause the transmittance to be lower. Thus, the liquid crystal display 100 can implement a high image sharpness, transmittance and smaller design all together.
In this connection, the polarization of light to be projected into the liquid crystal display depends upon the light incidence angle formed in relation to the direction of alignment of liquid crystal molecules filled in the LCD panel. More specifically, straight polarized light obliquely incident into the LCD panel goes out as elliptic polarized light due to the birefringence of the liquid crystal, so that only a part of the light supposed to go out will go out, resulting in a lower contrast. Especially the micro lens array provided in the liquid crystal display will cause incident light to be scattered onto the liquid crystal layer at an increased angle, which will result in an extremely low contrast.
An optical compensation technique to improve the image contrast in the liquid crystal display has been proposed in the Japanese Patent Laid Open No. 2001-174776 (Patent Document 2). The optical compensation technique disclosed in this Patent Document 2 is such that an optical compensation film having such an optical characteristic as to cancel the influence of the birefringence of the LCD panel is provided in the liquid crystal display to inhibit the image contrast from varying depending upon the incidence angle of light, namely, the so-called dependence of the contrast on the angle of visibility. The optical compensation film can compensate the phase difference for light incident at an extreme angle as well, so that the image contrast can be improved by applying this technique to a liquid crystal display having a micro lens array provided therein.
For information's sake, the effect of improvement in angle of visibility by the optical compensation element such as the optical compensation film is disclosed in the “Liquid Crystal—Technique for Increasing Angle of Visibility of TFT-LCD by Discotic Optical Compensation Film—Vol. 16, No. 1”.
Since the micro lenses used in the conventional liquid crystal projector are designed to provide optimum conditions for the transmittance, a combination of the micro lenses and optical compensation elements cannot assure any optimum contrast as the case may be. A design value for a micro lens which assures a high transmittance is disclosed in the Japanese Patent Laid Open No. 86901 of 1996 (Patent Document 3), for example. In the disclosed technique, however, major consideration is given to the transmittance.